• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Different cylinder heads, rockers & bump sticks for use on the 6.5

EWC said:
What does air flow thru the intake and exhaust ports have to due with IDI precups ?
Click to expand...

This is my take on the IDI:

Because of it's design your adding a in/out action into the compression/power strokes of the IDI making it overall less efficient than a DI diesel.

The addition of a blower/supercharge/turbo (s) has proven to be the most effective way around the issue and in all the decades of the IDI very few individuals ventured into the cylinder head ports now some bold individuals on this site are.

When considering VE the average of % loss inherent in the IDI design must be considered and higher rpm levels is needed along with a turbo that can flow the kind of CFM needed along with additional fueling to produce good hp/tq levels up top in the generally low rpm 6.5 IDI.

Mercedes high rpm 3.0 24 valve IDI is the most efficient on the market.

I'm by no means an expert on this topic and for more in-depth tech on the topic can be found in the tech postings on this site.
 
The bigger valves can be installed,mat a greater risk of cracking the heads. You need to be in the serious power and money range to play with that.
That's what the above "would it be ok for daily street use" back and forth was. Bill Heath did it on his lsr truck, and said its not reliable enough for it for fear of failure. Understand my differing opinion isn't so just with just Fellow Traveler, but Bill Heath, as he did it and stated it.
Problem is I had a friend do it here (Vegas) too. He sold the truck after several months of daily driving, so no idea how long it really lasted. The guy that bought the truck promised to stay in contact with us but never did. Somewhere out there is a black 1500 with a very modified engine, probably scraped by now. If you see it, you'll know it- 6" chopped top, frame rides 1" off the ground.

The rear coolant passages have been tried for more flow, it turns out doing it stalls water flow in the head and block in the middle and devistates them. Heath used to sell a kit and to his credit, once he learned of the problem with it stopped selling and never looked back. Some con artists out there still sell the kit. Good that your thinking about improvement options though, and better that you ask before you experiment and find the same errors we did .

Ho water pump with duramax fan and he fanclutch is the cooling answer, along with proper t stat, and a clean radiator stack. Then the top it off Evans waterless coolant seems to be magic.
 
Forget about the Mercedes , I'm talking about airflow only . Not IDI vs DI , 4 valve vs 2 valve or NA vs turbo , only airflow . Again , what does the airflow have to do with precups ?
 
Well, hard to not compare Idi vs di. A di uses less real estate in the head, so you can have bigger valves, or more area you can cut out. The precup gets in the way, and no real way to fix that.

Outside that a cross flow design (like motorcycle) allows a lot of room for enlargement and increased flow. So too does Uniflow, which is 1 on side like motorcycle, and 1 on top-like 71 series Detroit. (Perkins built an Idi for only 1 year that was this style. Under built crank mains so they ditched it- that's the one I built for Carroll Shelby in his diesel Shelby. HUGE MISTAKE Perkins walking away from it.)

The next thing is a bunch of people don't call them precup, or precumbustion chambers. They are SWIRL cup or SWIRL chambers. As the injected fuel hit it, it's design, along with air flow characteristics in the cylinder causes the misted fuel to swirl out causing an amazing dispersment for a very even burn. Instead of burning from precup area to the opposite side, the flame front will ignite half the cylinder area at once, then flame front travels only half the area to complete the burn. (That's what multi spark plug gassers are trying to accomplish on the simotaneous fired ones.) IMO altering the intake air can't have much effect on this, but some of the "head experts" do. I think it has far more to do with how you port the precup when enlarging it, making sure to keep the same geometry is critical, again IMO.

Last is intended design. Idi was chosen for mpg and low build cost by GM. Air flow concearn isn't high on the list in that arena.

I'm not sure if that helps. It hard to separate the components. Like what does a cam have to do with compression. Physically nothing. How it all works together is what matters. More air flow = more power, but not always more mpg.
 
EWC said:
Forget about the Mercedes , I'm talking about airflow only . Not IDI vs DI , 4 valve vs 2 valve or NA vs turbo , only airflow . Again , what does the airflow have to do with precups ?
Click to expand...
IMHO, the precups and chamber take up space that otherwise could be used for porting. When I say porting "I don't mean porting then checking on flow bench without doing pulls on rollers as the work progresses because increased flow is not all there is in the equation."

The following link is perhaps the best advice for any quality porting job; http://rehermorrison.com/tech-talk-70-airflow-fallacies-avoiding-the-pitfalls-of-the-flow-bench/
 
Last edited:
sctrailrider said:
I think ya'll missed something about heath's lsr, they CUT the valve angle's directly into the head, not a hardened seat, so the existing hard surface was cut away.. that is why the head wouldn't be a good dd set, because they would wear so fast....
Click to expand...

YEP! I totally missed that. We did a chopped precup and added new seats. Did not play with valve angle. Now I really wish I could look at those heads I detail. I wonder how many hours he has on them, if it's the original set.
 
I think you guys are missing my point and that is you can't change the design of the head . Precups are part of this head and we have to deal with it . Can't move them or delete them , deal with it . They don't take up space and I'm not sure the sizes of the valves would change that much as this is a small engine operating at lower speeds . They have nothing to due with airflow thru the intake ports . After the air is in the cylinder , that is when they come into play . And even then the opinions expressed here do not get their importance or design right . They do not cause swirl in the cylinder but do so in the chamber . That is why the " eyebrows " are cut into the pistons and aimed at the slot in the precup . After the fuel is ignited , do you really think the chamber directs this force in any direction ? The ignited fuel is looking for anyway to expand and the size of the slot does help with that expansion .

The cam most definitely has an affect on compression , choose one with much more duration after BDC and check your compression readings . You effectively shortened the compression stoke and that will change the readings .

The point of all this is porting . My porter did not care if it was a diesel head or gas , he was just working on airflow . You should too .
 
EWC said:
The point of all this is porting . My porter did not care if it was a diesel head or gas , he was just working on airflow . You should too .
Click to expand...

As I pointed out before "porting for airflow w/o dyno pull or run at track as the porting progresses is not conducive to good results." Your ill conceived notion of porting just for air flow is your opinion my opinion is it is a waste and the pros think so too.

AGAIN SEE: http://rehermorrison.com/tech-talk-70-airflow-fallacies-avoiding-the-pitfalls-of-the-flow-bench/
 
I wonder how well 1982 "J" cylinder heads (if they can be found) with their larger valves would do on a boosted 6.5 build using the newer cooling system design and EVANS waterless coolant.
 
Search the write ups. It's been done by several people. The precup has to change, and the injector to manifold clearance spaced if using regular truck side mount turbo. Slower off the bottom end, better top end... Slightly. About the same as jumping to 3" crossover and 4"'straight pipe from stock exhaust.

The larger valve is around 5%, but not the over all flow. But you can port the smaller valved heads to a better flow angle than 5%. If you stumble into a set, give it a shot, just a couple of gaskets and a weekend or two.
 
Will L. said:
Search the write ups. It's been done by several people. The precup has to change, and the injector to manifold clearance spaced if using regular truck side mount turbo. Slower off the bottom end, better top end... Slightly. About the same as jumping to 3" crossover and 4"'straight pipe from stock exhaust.

The larger valve is around 5%, but not the over all flow. But you can port the smaller valved heads to a better flow angle than 5%. If you stumble into a set, give it a shot, just a couple of gaskets and a weekend or two.
Click to expand...
For a small gain hot worth the effort...
 
FellowTraveler said:
For a small gain hot worth the effort...
Click to expand...

I'm curious FT, how much of a gain is anything worth doing if someone is searching for what "could be their"...

When does effort pay off ??

So 5% isn't worth much, would 10% make a difference, maybe 15% ... it depends on the person and just how much they want to spend to TRY ....

I remember some years ago different turbos & such were down played here and other forums... well that has changed as folks started looking for something better...

I am one that doesn't mind taking the time to try things that don't come in a box, I like "one off" things and I admire those that are willing to at least TRY something different even if later it doesn't work out like once thought... that's the testing part.

There isn't a engine dyno setup for a 6.x diesel anywhere that I know of YET, so the testing part takes a long time to gather as many facts as possible then the entire build can be looked at for places to investigate.

I truly think every gain is worth looking into, no mater how small.. will everyone think this way... naw, maybe 1% will, at only 1% of people maybe we should just quit looking for anything better in this platform..naw, they didn't quit they came out with the p400 platform instead...
 
We have flow numbers for the 82 J head W/larger valves... their was increased flow in the low lift area but over all flow at the higher lifts were the same so only low lift was better than later stock heads..
 
I have another question for the masses....

Someone mentioned the rear cooling ports and much talk has been going on in the years past, well I wonder if their is another place to look at cooling and moving water through the motor...

Again, I like to travel where not many others have, so I ask this to everyone.....

Has anyone ever taken a close look at the heads, specifically the outside of the head just under the intake port???

Ever notice the small plugs directly under the port ? Well, if you take a close look at the cut away pics I have posted you will notice that a plug fills a water passage that has on exit, it is lower than the highest point on the head and air will stay there and not coolant, that passage goes directly to the area between the valves, could this be helping the cracking trouble, me thinks yes....

My fix... tap those passages and route that coolant flow out to the top hose with 1/8 tube & regulate it, this will do at the least two things, assist flow between the valves, and remove the air better from the heads..

This won't do squat for any gains in HP, but just might help with a motor that's working hard and IS making more heat than stock trim....

This falls into the 1% area, some will think it's a good idea, others not so much, still others will pass and look for something someone is selling as a quick fix instead... such is life ....
 
Really Traveler ? You post an article from David Reher and think he is the first one to talk about porting ? You know nothing about how my heads were ported , who did them , sizing , etc and yet you can judge them ? Blanket statements will get you in trouble and you continue to stick your foot in your mouth . I posted my results because like a lot off people on here , I just like the 6.2 and tinkering with . Don't really care if you think you are the One and Only , your opinion is yours . Don't like what I post , don't read it . Some may read and learn , others may not .
 
Ok Rider , I agree with what you are saying about the 1% . Don't know if you are aware of it but the holes between the valves , for cooling , can be sleeved/repaired for the cracks and possibly used . The plates were talked about a long time ago and Heath thought it helped with cooling to run hoses . The GM design turned out to be the best . Use it , the dual thermostats and high flow waterpump . Don't use just one thermostat , as it will build more pressure and could blow freezeplugs . There are a couple of high flow pumps , with different fans , so do some research .

If I was in your shoes , I would be looking at doing/porting an intake manifold . The stock intake flows less than what you have in the heads , anything put on them will be a choke .

Views/opinions are mine , waiting for approval from FT .
 
sctrailrider said:
I'm curious FT, how much of a gain is anything worth doing if someone is searching for what "could be their"...

When does effort pay off ??

So 5% isn't worth much, would 10% make a difference, maybe 15% ... it depends on the person and just how much they want to spend to TRY ....

I remember some years ago different turbos & such were down played here and other forums... well that has changed as folks started looking for something better...

I am one that doesn't mind taking the time to try things that don't come in a box, I like "one off" things and I admire those that are willing to at least TRY something different even if later it doesn't work out like once thought... that's the testing part.

There isn't a engine dyno setup for a 6.x diesel anywhere that I know of YET, so the testing part takes a long time to gather as many facts as possible then the entire build can be looked at for places to investigate.

I truly think every gain is worth looking into, no mater how small.. will everyone think this way... naw, maybe 1% will, at only 1% of people maybe we should just quit looking for anything better in this platform..naw, they didn't quit they came out with the p400 platform instead...
Click to expand...

Not knocking what you are doing with your R&D w/cylinder heads and yes any gains are good but lets be honest about the stock cylinder heads "they are well suited for excess of 400 hp" if there was something better aftermarket would have came out with it long ago. IMHO, you ahead of the game in your R&D because you cut the heads to see what your dealing with.

On the subject of turbos "not knowing exactly what a turbos specs are then tuning fuel delivery becomes a guessing game" at the very least. I've found CKO same part number turbos with different sized wheels and compressor housing so it's a crap shoot too. I'm going to Holset so I can manage to get a better tune the fuel delivery because they are throttled by fuel. If we were dealing with a throttle plate then there substantial gains to be had tinkering with intake manifold and throttle plate to intake valve distance.

What is the difficulty of adapting an engine dyno to the 6.5 td?
 
You must log in or register to reply here.
Back
Top